Meteorology is the interdisciplinary scientific study of the atmosphere that focuses on weather processes and forecasting (in contrast with climatology). Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the eighteenth century. The nineteenth century saw breakthroughs occur after observing networks developed across several countries. Breakthroughs in weather forecasting were achieved in the latter half of the twentieth century, after the development of the computer.

Meteorological phenomena are observable weather events which illuminate and are explained by the science of meteorology. Those events are bound by the variables that exist in Earth's atmosphere: They are temperature, air pressure, water vapor, and the gradients and interactions of each variable, and how they change in time. The majority of Earth's observed weather is located in the troposphere.[1][2] Different spatial scales are studied to determine how systems on local, region, and global levels impact weather and climatology. Meteorology, climatology, atmospheric physics, and atmospheric chemistry are sub-disciplines of the atmospheric sciences. Meteorology and hydrology compose the interdisciplinary field of hydrometeorology. Interactions between Earth's atmosphere and the oceans are part of coupled ocean-atmosphere studies. Meteorology has application in many diverse fields such as the military, energy production, transport, agriculture and construction.

History

In 350 BC, Aristotle wrote Meteorology.[3] Aristotle is considered the founder of meteorology.[4] One of the most impressive achievements described in the Meteorology is the description of what is now known as the hydrologic cycle.[5] The Greek scientist Theophrastus compiled a book on weather forecasting, called the Book of Signs. The work of Theophrastus remained a dominant influence in the study of weather and in weather forecasting for nearly 2,000 years.[6] In 25 AD, Pomponius Mela, a geographer for the Roman Empire, formalized the climatic zone system.[7] Around the 9th century, Al-Kindi (Alkindus), an Arab naturalist, wrote a treatise on meteorology entitled Risala fi l-Illa al-Failali l-Madd wa l-Fazr (Treatise on the Efficient Cause of the Flow and Ebb), in which he presents an argument on tides which "depends on the changes which take place in bodies owing to the rise and fall of temperature."[8] Also in the 9th century, Al-Dinawari, a Kurdish naturalist, writes the Kitab al-Nabat (Book of Plants), in which he deals with the application of meteorology to agriculture during the Muslim Agricultural Revolution. He describes the meteorological character of the sky, the planets and constellations, the sun and moon, the lunar phases indicating seasons and rain, the anwa (heavenly bodies of rain), and atmospheric phenomena such as winds, thunder, lightning, snow, floods, valleys, rivers, lakes, wells and other sources of water.[9]

Observation networks and weather forecasting

In 1654, Ferdinando II de Medici establishes the first weather observing network, that consisted of meteorological stations in Florence, Cutigliano, Vallombrosa, Bologna, Parma, Milan, Innsbruck, Osnabruck, Paris and Warsaw. Collected data was centrally sent to Florence at regular time intervals.[37] In 1832, an electromagnetic telegraph was created by Baron Schilling.[38] The arrival of the electrical telegraph in 1837 afforded, for the first time, a practical method for quickly gathering surface weather observations from a wide area.[39] This data could be used to produce maps of the state of the atmosphere for a region near the Earth's surface and to study how these states evolved through time. To make frequent weather forecasts based on these data required a reliable network of observations, but it was not until 1849 that the Smithsonian Institution began to establish an observation network across the United States under the leadership of Joseph Henry[40]. Similar observation networks were established in Europe at this time. In 1854, the United Kingdom government appointed Robert FitzRoy to the new office of Meteorological Statist to the Board of Trade with the role of gathering weather observations at sea. FitzRoy's office became the United Kingdom Meteorological Office in 1854, the first national meteorological service in the world. The first daily weather forecasts made by FitzRoy's Office were published in The Times newspaper in 1860. The following year a system was introduced of hoisting storm warning cones at principal ports when a gale was expected.

Numerical weather prediction

A meteorologist at the console of the IBM 7090 in the Joint Numerical Weather Prediction Unit. c. 1965

In 1904, Norwegian scientist Vilhelm Bjerknes first argued in his paper Weather Forecasting as a Problem in Mechanics and Physics that it should be possible to forecast weather from calculations based upon natural laws.[46]

It was not until later in the 20th century that advances in the understanding of atmospheric physics led to the foundation of modern numerical weather prediction. In 1922, Lewis Fry Richardson published "Weather Prediction By Numerical Process," after finding notes and derivations he worked on as an ambulance driver in World War I. He described therein how small terms in the prognostic fluid dynamics equations governing atmospheric flow could be neglected, and a finite differencing scheme in time and space could be devised, to allow numerical prediction solutions to be found. Richardson envisioned a large auditorium of thousands of people performing the calculations and passing them to others. However, the sheer number of calculations required was too large to be completed without the use of computers, and the size of the grid and time steps led to unrealistic results in deepening systems. It was later found, through numerical analysis, that this was due to numerical instability.

In the 1960s, the chaotic nature of the atmosphere was first observed and understood by Edward Lorenz, founding the field of chaos theory.[48] These advances have led to the current use of ensemble forecasting in most major forecasting centers, to take into account uncertainty arising from the chaotic nature of the atmosphere. In recent years, climate models have been developed that feature a resolution comparable to older weather prediction models. These climate models are used to investigate long-term climate shifts, such as what effects might be caused by human emission of greenhouse gases.

Equipment

Each science has its own unique sets of laboratory equipment. In the atmosphere, there are many things or qualities of the atmosphere that can be measured. Rain, which can be observed, or seen anywhere and anytime was one of the first ones to be measured historically. Also, two other accurately measured qualities are wind and humidity. Neither of these can be seen but can be felt. The devices to measure these three sprang up in the mid-15th century and were respectively the rain gauge, the anemometer, and the hygrometer.[51]

Sets of surface measurements are important data to meteorologists. They give a snapshot of a variety of weather conditions at one single location and are usually at a weather station, a ship or a weather buoy. The measurements taken at a weather station can include any number of atmospheric observables. Usually, temperature, pressure, wind measurements, and humidity are the variables that are measured by a thermometer, barometer, anemometer, and hygrometer, respectively.[52] Upper air data are of crucial importance for weather forecasting. The most widely used technique is launches of radiosondes. Supplementing the radiosondes a network of aircraft collection is organized by the World Meteorological Organization.

Remote sensing, as used in meteorology, is the concept of collecting data from remote weather events and subsequently producing weather information. The common types of remote sensing are Radar, Lidar, and satellites (or photogrammetry). Each collects data about the atmosphere from a remote location and, usually, stores the data where the instrument is located. RADAR and LIDAR are not passive because both use EM radiation to illuminate a specific portion of the atmosphere.[53] Weather satellites along with more general-purpose Earth-observing satellites circling the earth at various altitudes have become an indispensable tool for studying a wide range of phenomena from forest fires to El Niño.

Spatial scales

In the study of the atmosphere, meteorology can be divided into distinct areas of emphasis depending on the temporal scope and spatial scope of interest. At one extreme of this scale is climatology. In the timescales of hours to days, meteorology separates into micro-, meso-, and synoptic scale meteorology. Respectively, the geospatial size of each of these three scales relates directly with the appropriate timescale.

Other subclassifications are available based on the need by or by the unique, local or broad effects that are studied within that sub-class.

Microscale

Microscale meteorology is the study of atmospheric phenomena of about 1 km or less. Individual thunderstorms, clouds, and local turbulence caused by buildings and other obstacles, such as individual hills fall within this category.[54]

Mesoscale

Mesoscale meteorology is the study of atmospheric phenomena that has horizontal scales ranging from microscale limits to synoptic scale limits and a vertical scale that starts at the Earth's surface and includes the atmospheric boundary layer, troposphere, tropopause, and the lower section of the stratosphere. Mesoscale timescales last from less than a day to the lifetime of the event, which in some cases can be weeks. The events typically of interest are thunderstorms, squall lines, fronts, precipitation bands in tropical and extratropical cyclones, and topographically generated weather systems such as mountain waves and sea and land breezes.[55]

Synoptic scale

Synoptic scale meteorology is generally large area dynamics referred to in horizontal coordinates and with respect to time. The phenomena typically described by synoptic meteorology include events like extratropical cyclones, baroclinic troughs and ridges, frontal zones, and to some extent jet streams. All of these are typically given on weather maps for a specific time. The minimum horizontal scale of synoptic phenomena are limited to the spacing between surface observation stations.[56]

Annual mean sea surface temperatures.

Global scale

Global scale meteorology is study of weather patterns related to the transport of heat from the tropics to the poles. Also, very large scale oscillations are of importance. Those oscillations have time periods typically longer than a full annual seasonal cycle, such as ENSO, PDO, MJO, etc. Global scale pushes the thresholds of the perception of meteorology into climatology. The traditional definition of climate is pushed in to larger timescales with the further understanding of how the global oscillations cause both climate and weather disturbances in the synoptic and mesoscale timescales.

Numerical Weather Prediction is a main focus in understanding air-sea interaction, tropical meteorology, atmospheric predictability, and tropospheric/stratospheric processes.[57]. Currently (2007) Naval Research Laboratory in Monterey produces the atmospheric model called NOGAPS, a global scale atmospheric model, this model is run operationally at Fleet Numerical Meteorology and Oceanography Center. There are several other global atmospheric models.

Some meteorological principles

Boundary layer meteorology

Boundary layer meteorology is the study of processes in the air layer directly above Earth's surface, known as the atmospheric boundary layer (ABL). The effects of the surface – heating, cooling, and friction – cause turbulent mixing within the air layer. Significant fluxes of heat, matter, or momentum on time scales of less than a day are advected by turbulent motions.[58] Boundary layer meteorology includes the study of all types of surface-atmosphere boundary, including ocean, lake, urban land and non-urban land.

Dynamic meteorology

Dynamic meteorology generally focuses on the fluid dynamics of the atmosphere. The idea of air parcel is used to define the smallest element of the atmosphere, while ignoring the discrete molecular and chemical nature of the atmosphere. An air parcel is defined as a point in the fluid continuum of the atmosphere. The fundamental laws of fluid dynamics, thermodynamics, and motion are used to study the atmosphere. The physical quantities that characterize the state of the atmosphere are temperature, density, pressure, etc. These variables have unique values in the continuum.[59]

Applications

Weather forecasting

Forecast of surface pressures five days into the future for the north Pacific, North America, and north Atlantic ocean.

Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location. Human beings have attempted to predict the weather informally for millennia, and formally since at least the nineteenth century.[60][61] Weather forecasts are made by collecting quantitative data about the current state of the atmosphere and using scientific understanding of atmospheric processes to project how the atmosphere will evolve.[62]

Once an all human endeavor based mainly upon changes in barometric pressure, current weather conditions, and sky condition,[63][64]forecast models are now used to determine future conditions. Human input is still required to pick the best possible forecast model to base the forecast upon, which involves pattern recognition skills, teleconnections, knowledge of model performance, and knowledge of model biases. The chaotic nature of the atmosphere, the massive computational power required to solve the equations that describe the atmosphere, error involved in measuring the initial conditions, and an incomplete understanding of atmospheric processes mean that forecasts become less accurate as the difference in current time and the time for which the forecast is being made (the range of the forecast) increases. The use of ensembles and model consensus help narrow the error and pick the most likely outcome.[65][66][67]

There are a variety of end users to weather forecasts. Weather warnings are important forecasts because they are used to protect life and property.[68] Forecasts based on temperature and precipitation are important to agriculture,[69][70][71][72] and therefore to commodity traders within stock markets. Temperature forecasts are used by utility companies to estimate demand over coming days.[73][74][75] On an everyday basis, people use weather forecasts to determine what to wear on a given day. Since outdoor activities are severely curtailed by heavy rain, snow and the wind chill, forecasts can be used to plan activities around these events, and to plan ahead and survive them.

The effects of ice on aircraft are cumulative-thrust is reduced, drag increases, lift lessens, and weight increases. The results are an increase in stall speed and a deterioration of aircraft performance. In extreme cases, 2 to 3 inches of ice can form on the leading edge of the airfoil in less than 5 minutes. It takes but 1/2 inch of ice to reduce the lifting power of some aircraft by 50 percent and increases the frictional drag by an equal percentage.[77]

Agricultural meteorology

Meteorologists, soil scientists, agricultural hydrologists, and agronomists are persons concerned with studying the effects of weather and climate on plant distribution, crop yield, water-use efficiency, phenology of plant and animal development, and the energy balance of managed and natural ecosystems. Conversely, they are interested in the role of vegetation on climate and weather.[78]

Hydrometeorology

Hydrometeorology is the branch of meteorology that deals with the hydrologic cycle, the water budget, and the rainfall statistics of storms.[79] A hydrometeorologist prepares and issues forecasts of accumulating (quantitative) precipitation, heavy rain, heavy snow, and highlights areas with the potential for flash flooding. Typically the range of knowledge that is required overlaps with climatology, mesoscale and synoptic meteorology, and other geosciences.[80]

^ Many attempts had been made prior to the 15th century to construct adequate equipment to measure the many atmospheric variables. Many were faulty in some way or were simply not reliable. Even Aristotle notes this in some of his work; as the difficulty to measure the air.

^ An international version called the Aeronautical Information Publication contains parallel information, as well as specific information on the international airports for use by the international community.

External links

Air Quality Meteorology - Online course that introduces the basic concepts of meteorology and air quality necessary to understand meteorological computer models. Written at a bachelor's degree level.

The GLOBE Program - (Global Learning and Observations to Benefit the Environment) An international environmental science and education program that links students, teachers, and the scientific research community in an effort to learn more about the environment through student data collection and observation.

Glossary of Meteorology - From the American Meteorological Society, an excellent reference of nomenclature, equations, and concepts for the more advanced reader.

Temperature and heat
exchange processes

Identify the effect of changes in temperature on volume,
density, state of matter, and gasses.

State the units of measurement of temperature.

State the usual height at which the surface air temperature is
measured.

Define ‘radiation’ (as this applies to meteorology).

Explain the effect of emitting or receiving radiation on the
temperature of a body or gas.

Explain the relationship between the temperature of an emitting
substance and the:

(a) associated electromagnetic energy wavelength/frequency;

(b) type of radiation (spectrum).

Describe the characteristics of solar radiation.

State the atmospheric constituents that absorb, reflect or
scatter all, or part of, solar radiation.

Define:

(a) sky radiation;

(b) global solar radiation.

List and explain the three main factors that influence the
amount of solar energy received by the earth.

Describe the characteristics of terrestrial radiation.

Explain the relationship between solar radiation, terrestrial
radiation and warming/cooling of the atmosphere.

List the substances that absorb terrestrial radiation, and
explain the consequence of this absorption on global air
temperature.

Define ‘atmospheric window’.

Define ‘energy budget’.

Describe the process of conduction.

Describe the process of convection.

Define ‘sensible heat’.

Define ‘latent heat’.

Describe ‘diurnal variation of surface air temperature’.

Explain the effects of the following factors on the diurnal
variation of surface air temperature:

(a) type of surface;

(b) oceans and other large water areas;

(c) water vapour;

(d) cloud;

(e) the wind.

Define ‘specific heat’.

Interpret the curves of the diurnal variation of surface air
temperature over a 24 hour period which reflects the factors listed
in 20.6.44.

Describe the basic principles and methods through which heat
transfer takes place globally.

Describe the main characteristics of the following climates:

(a) oceanic;

(b) maritime;

(c) continental.

Atmospheric moisture

Define:

(a) condensation;

(b) evaporation;

(c) precipitation;

(d) melting;

(e) freezing;

(f) sublimation;

(g) deposition;

(h) adiabatic process;

(i) super saturation.

Describe and explain the condensation process and the main
methods through which condensation occurs.

Describe the function of condensation nuclei in the condensation
process.

Describe the deposition process.

Describe the evaporation process.

Explain what is meant by ‘partial pressure’ of a gas.

Explain what is meant by ‘saturation vapour pressure of moist
air’.

Describe the effect of ice surfaces, and high atmospheric
temperatures, on the saturation vapour pressure of moist air.

Explain the function of latent heat in the condensation and
evaporation processes.

Describe how temperature, water content of air, the wind, and
atmospheric pressure influence the rate of evaporation.

State six processes through which water can alter its state and
explain whether

Explain the relationship between density of water, temperature
and volume.

Explain what is meant by the terms:

(a) absolute humidity;

(b) humidity mixing ratio;

(c) saturation content;

(d) relative humidity.

Describe the relationship between absolute humidity, air
temperature, and relative humidity.

Describe the diurnal variation of relative humidity.

Define ‘dew point’.

Explain how water content and altitude influence the value of
the dew point.

Describe the relationship between absolute humidity, air
temperature, relative humidity and dew point.

Explain the method of operation of the:

(a) wet bulb/dry bulb hygrometer;

(b) hair hygrometer;

(c) lithium chloride element.

Describe the effect of moisture content on the density of
air.

The wind

State the four forces that have a fundamental influence on the
wind velocity.

Explain the principle of Coriolis force on moving air.

State the:

(a) variation of the magnitude of Coriolis force with
latitude;

(b) direction of Coriolis force relative to the flow of air.

Explain the effect of Coriolis force and pressure gradient on
the movement of air relative to the isobars.

Describe the inter-relation between pressure gradient, Coriolis
force and centrifugal (cyclostrophic) force on the curvature of the
isobars around high and low pressure systems in the Southern
Hemisphere.

Define:

(a) gradient wind;

(b) geostrophic wind.

Explain how stability, wind strength and surface roughness
affect the friction layer near the earth's surface.

Describe the vertical variation of wind speed and direction in
the friction layer.

Describe the diurnal variation of the surface wind in the
Southern Hemisphere.

Define:

(a) backing of the wind;

(b) veering of the wind.

Describe the change in wind velocity when climbing out of, or
descending into, the friction layer.

With regard to the rotating cup anemometer:

(a) describe the principle of operation;

(b) state the function it performs;

(c) state the usual height at which the surface wind is
measured.

State the approximate wind strength indicated by a 25-knot
windsock when at 30°, 45°, 75°, and 90 degrees from the
vertical.

Describe how an approximate wind direction can be determined
from:

(a) ripples on water;

(b) wind lanes on water;

(c) wind shadow.

State Buys Ballot’s law.

Describe the application of Buys Ballot’s law on determining
areas of high and low pressure, and on establishing possible errors
in altimeter reading.

Define ‘wind shear’.

Describe the effect of vertical and horizontal wind shear on
aircraft operations.

Stability of
air

Explain how the adiabatic process affects the temperature of
rising and descending parcels of air.

Define: (a) stable air;

(b) unstable air;

(c) neutrally stable/unstable air.

Describe the weather characteristics of:

(a) stable air;

(b) unstable air.

Describe how stable and unstable air affect flying
conditions.

State the two main factors that determine whether air will be
stable or unstable.

Describe what is meant by ‘environment lapse rate (ELR)’.

Using graphs:

(a) describe steep and shallow ELRs;

(b) define and describe ‘inversion’ and ‘isothermal layer’.

Define ‘adiabatic process’.

Define ‘dry adiabatic lapse rate’ (DALR).

State the value of the average DALR.

Interpret graphs comparing the DALR against altitude and
temperature, and identify the temperature changes in rising and
descending parcels of unsaturated air.

Comparing ELR against DALR, explain how the stability or
instability of rising and descending 'dry' air can be
determined.

Define ‘saturated adiabatic lapse rate’ (SALR).

State the value of the average SALR.

Explain why the SALR steepens with altitude.

Comparing ELR against SALR, explain how the stability or
instability of rising and descending saturated air can be
determined.

From LoveToKnow 1911

From Wikibooks, the open-content textbooks
collection

Current
revision (unreviewed)

About the
Book

Most people assume meteorology to be weather, or vise versa.
Most people think that you can easily look at some pictures and say
what the weather will most likely be. Both of these statements are
wrong. When you want to understand meteorology, you have to
understand the atmosphere, some physics, and a lot of charts. In
this book, I will try and open people's world to meteorology, but
that does mean learning a lot of other topics that may seem to have
nothing to do with weather or climate. If you stick with me, I will
do my best to make sure it stays on topic and doesn't go in depth
on other topics without actually needing to. For example, I will
not throw handfuls of physics formulas at you, but instead simply
cover what you need to know and go from there.

The book was originally a small set of articles talking about
random points of meteorology. Of course, you can not talk about one
thing without talking about another, this made the articles hard to
read and understand. Hopefully, in time and with the help of
others, this book will become useful for anyone looking for a piece
of information they forgot a long time ago or are just curious.

Further
Reading

Meteorology is a branch of atmospheric physics that focuses on air pressure, the climate, temperature and weather prediction. People who practice meteorology are called meteorologists. It is also a major branch of earth science.frr:Wääderkunde